The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Many modern motor vehicle manually shifted transmissions utilize controlled hydraulic fluid to engage or disengage a clutch during transmission gear shifting. A clutch pedal is positioned proximate to a vehicle brake pedal in a driver side compartment of the motor vehicle and may include a rigid rod extending from the clutch pedal through a firewall and into an engine compartment of the motor vehicle. A hydraulic fluid line, also designated as a clutch release line, is routed through the engine compartment from a clutch master cylinder to a clutch slave cylinder.
Vehicle and engine vibrations, particularly those associated with the engine and transmission may transfer via the clutch release line to the clutch pedal. System vibrations in a frequency ranging between approximately 50 Hz to approximately 225 Hz may be “felt” by the vehicle operator during clutch pedal operation. These vibrations are undesirable as they lead to a generally negative interpretation of vehicle ride quality.
Attempts have therefore been made to reduce hydraulic clutch release line vibration that is transferred to the clutch pedal. Such attempts include adding features in the clutch release line to absorb or attenuate hydraulic system vibration, including use of a diaphragm attenuator, or a hydraulic de-coupler. Known diaphragm attenuators have a fluid chamber within which is positioned a flexible metal or resilient material diaphragm which absorbs hydraulic fluid energy and thereby attenuates vibration. Such diaphragm attenuators provide incremental improvement in vibration attenuation over a non-attenuated system, but do not achieve a desirable attenuation (approximately 20 dB attenuation), plus they add component parts that may wear over time. Also known to help attenuate clutch release line and clutch pedal vibration are hydraulic de-couplers. Known hydraulic de-couplers include multiple components including releasable body halves and internal moving parts which displace to attenuate hydraulic vibration. Such de-couplers are more effective in achieving vibration attenuation than known diaphragm attenuators, but are expensive and have moving component parts that also may wear over time.